Rectifying system



1937- H. WINOGRAD' 2,068,970

BBCTIFYING SYSTEM Filed Aug. 7, 1933 4 Sheets-Sheet l Jan. 26, 1937. H. WINOGRAD 'RECTIFYING SYSTEM Filed Aug. '7, 1933 4 Sheets-Sheet 2 a fi I l l l lh 4 Sheets-Sheet 5 H. WINQGRAD I RECTIFYING SYSTEM Filed Aug. 7, 1936 Jan. 26, 1937.

Jan. 26, 1937.

H. WINOGRAD 2,068,970 RECTIFYING SYSTEM Filed Aug. 7, 1935 4 Sheets-Sheet 4 Patented Jan. 26, 1937 UNITED STATES PATENT OFFICE Allis-Chalmers Manufacturing Company,

Mil-

waukee, Wis., a. corporation of Delaware Application August 7,

17 Claims.

This invention relates to regulating systems and more particularly to a system for gradually initiating the flow of current in an electric current consuming circuit.

In electric systems comprising current generating, converting or consuming means, a sudden establishment of a flow of current therethrough at full load value is not generally permissible but such establishment must be effected gradually to avoid operating troubles of a nature dependent upon the nature of the means employed in the system. For instance, the flow of current through a direct current generator supplying current to electrolytic cells must be progressively established to avoid sparking at the commutator of the generator and also to permit the cells to become gradually polarized. The current flowing through electric motors must also be limited at starting by suitable means until the counterelectromotive force of the motor becomes sufficient to maintain the current within the permissible limits. When the flow of current occurs through an electron discharge device, during the starting period the device is generally not at the most favorable conditions of pressure, temperature and ionization required for the trouble-free flow of full load current therethrough. The current must therefore be established gradually in time and, in addition, it is also advantageous to regulate the flow of current during normal operation in response to conditions other than time or electrical conditions, such as conditions of pressure and temperature.

It is therefore among the objects of the present invention to provide a system for controlling the fiow of current through current conducting means in response to conditions other than electrical conditions of such means.

Another object of the present invention is to provide a system for progressively increasing the flow of current through current conducting means after initiation of such fiow of current.

Another object of the present invention is to provide a system for progressively establishing the flow of current through an electron discharge device.

Another object of the present invention is to provide a system for regulating the flow of current through an electron discharge device in response to the pressure conditions within such device.

Another object of the present invention is to provide a system for regulating the flow of current through an electron discharge device in response to temperature conditions of such device,

1933, Serial No. 683,939

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 diagrammatically illustrates one embodiment of the present invention applied to the control of an electric current rectifier in which a constant flow of current is automatically established in stepwise manner;

Fig. 2 diagrammatically illustrates a modified embodiment of the present invention in which the flow of current is first gradually established and is thereafter maintained at constant voltage during normal operation of the rectifier;

Fig. 3 diagrammatically illustrates another modified embodiment of the present invention in which the flow of current is both gradually established and regulated, during normal operation, in response to the temperature of the rectifier; and

Fig. 4 diagrammatically illustrates a. further modified embodiment of the present invention in which the flow of current is gradually established and is also regulated in. response to the pressure within the rectifier.

Each of the figures of the drawings shows a difierent combination of difierent control elements but it will be understood that elements taken from different figures may be combined to form a system without departing from the spirit of the invention.

Referring more particularly to the drawings by characters of reference, reference number 6 designates an alternating current line of any number of phases operating at any suitable voltage and frequency and herein represented as a three phase line. Assuming that current received from line 6 is to be converted into direct current to be supplied to a direct current line having a negative conductor 1 and a positive conductor 8. To obtain this effect, line 6 is connected with the primary winding 9 of a transformer having a secondary winding H comprising a plurality of star connected phase displaced portions forming a neutral point connected with conductor 1. The several portions of winding l l are severally connected with the anodes l2 of an electron discharge device B of any suitable type having a cathode it connected with conductor 8. Device 13 is provided with the usual discharge igniting and maintaining means (not shown) and with any other auxiliary equipment necessary for the operation thereof such as the well known coolmg and evacuating means, which are not directly afiected by the system. illustrated in Fig. 1 and are therefore not shown in such figure. Discharge device I3, which will hereinafter be referred to as rectifier I3 for the sake of brevity, is provided with suitable discharge controlling means such as control electrodes I5 severally associated with the anodes I2. Each control electrode I6 is connected through a resistor I! with one of the star connected phase displaced portions of the secondary winding I8 of a control transformer having a primary winding I9 energized from line 6 through reactors 2 I. The operation of control electrodes It is regulated by means of a regulator generally designated by numeral 22 and comprising a plurality of star connected variable resistors 23 severally connected with the terminals of winding I9. The amount of resistance of resistors 23 in circuit is automatically adjusted in response to the flow of current through winding 9 by means of a current transformer 24 connected with the windings of a torque producing element 26 which effects the displacement of the movable connections of resistors 23 against the action of a spring 21. The windings of torque element 23 are shunted by resistors 28, 29 and SI. The flow of current through rectifier I3 is preferably initiated by closure of a circuit breaker 32 connecting cathode I4 with conductor 8. Such circuit breaker is provided with auxiliary contacts 33 controlling the connection of a suitable source of current such as a battery 34 with the coil of a time delay relay 35 operable to short circuit resistor 28. Relay 35 also controls the connection of battery 34 with the coil of a second time delay relay 36 operable to short circuit resistor 29.

As a result of the above connections, rectifier I3 constitutes the current conductive means and, more particularly, the electron discharge means to be controlled, control electrodes I6 constitute the discharge controlling means and regulator 22 regulates the flow of current through the discharge means in response to an electrical condition of the system which, in the present embodiment, is the magnitude of the flow of current in winding 9. Assuming that the arc igniting and maintaining means have operated, the flow of current through the discharge means to a load (not shown) is initiated by means of circuit breaker 32. Relays 35 and 36 operate in response to an operating condition of the system other than an electrical condition thereof, such condition being the movement of circuit breaker 32, for automatically controlling the flow of current through rectifier I3. Such flow of current is limited, in time, at increasing values following closure of circuit breaker 32 by Varying the adjustment of regulator 22 in time to vary the action thereof. Relays 35 and 36 are directly controlled by circuit breaker 32 to progressively establish the fiow of current upon operation of the circuit breaker.

In operation, therefore, line 6 being energized and the system being in the position shown in Fig. 1, closure of circuit breaker 32 will cause the flow of current from line 6 through rectifier I3 to line I, 8 provided that the voltages of winding I8 are of the proper magnitudes and phases relative to the voltages of winding II as is well known in the art. Such fioW of current causes current transformer 24 to supply a corresponding current to the windings of torque element 26, a minor portion of such current flowing through resistors 28, 29 and 3|. If the load connected with line I, 8 is such as to initially draw a current having a magnitude below a predetermined limit, no operating trouble is to be expected from the fiow of such current through rectifier I3 and regulator 22 is therefore so adjusted as to remain in the position shown, thus leaving the flow of current through rectifier I3 unregulated. If the flow of current through rectifier I3 exceeds such predetermined limit, the torque of element 26 overcomes the torque of spring 21 to cause a displacement of the connections of resistors 23. Such resistors are then partially short circuited and receive, from line '6, an increasing amount of current which flows through reactors 2I and cause an increasing reactive voltage drop to occur therein. Such increased leading voltage drop causes the voltages of windings l9 and I8 to lag, thereby retarding the times of positive energization of control electrodes I6 with respect to cathode I 4 in the voltage cycle of line 6, and causing the flow of current through rectifier I3 to be decreased as is well known. Such action continues until the flow of current is regulated to the predetermined desired value and the regulator thereafter remains in the position reached thereby until change of load causes further regulating operation of the regulator to maintain the flow of current at the predetermined value. Closure of circuit breaker 32 also causes the coil of relay 35 to be energized from battery 34 through contacts 33 and, after a predetermined period of time, relay 35 short circuits resistor 28. The windings of torque element 26 thereupon receive a lesser portion of current from transformer 24 and regulator 22 will therefore regulate the flow of current through rectifier I3 to a correspondingly greater value. Operation of relay 35 also energizes the coil of relay 36 and, after another predetermined length of time, relay 36 short circuits resistor 29, thereby causing a still lesser portion of the current of current transformer 24 to fiow through the coils of torque element 26. The fiow of current through rectifier I3 is then adjusted to the value desired for normal operation at which value it is thereafter constantly maintained, and the starting operation is then terminated. If, however, the current taken by the load is less than the predetermined value, the regulator is ineffectual but remains operable to limit such current to the predetermined value when changes in load condition cause the flow of such current to increase.

In the embodiment illustrated in Fig. 2, the action of control electrodes I6 is regulated by a modified regulator 37 provided with a resistor 38 having a movable tap actuated by a torque element 39 and acting against spring 27. Resistor 1 38 is connected with conductor 1 through a rheostat M and with cathode I4 through a resistor 42. Resistors 38 and 42 and rheostat 4| constitute an adjustable voltage divider by means of which a variable portion of the voltage of line "i, 8 is impressed between cathode I 4 and the neutral point of winding I8 by the connection of such neutral point with the movable tap of resistor 38. Such neutral point may also be connected with cathode I4 through a capacitor 43 for the purpose of reducing the harmonic alternating current Voltage components resulting from the flow of alternating current components through resistors 42 and 38. The armature of torque element 39 is provided with a coil 44 connected in series with a rheostat 46 between conductor I and cathode I4. The field of torque element 39 is provided with a voltage coil 41 connected with conductor 7 through a rheostat 48 and with a current coil 49 connected with one terminal of a shunt 52 receiving the current flowing through cathode I4. In the present embodiment, contacts 33 control the connection of battery 34 with a limit switch 53 and with one field coil 54 and the armature 56 of a motor 55. Circuit breaker 32 is provided with a second pair of contacts 51 controlling the connection of battery 34 with a resistor 58, a second limit switch 59, a second field coil 6i and the armature 56 of motor 55. Field coils 54 and 6| are so wound as to cause motor 55 to rotate in the one or in the other direction upon closure of contacts 33 or 51. Motor 55 drives the arm 63 of a rheostat 62, such arm controlling the limit switches 53 and 59 to cause motor 55 to stop when such arm has reached the one or the other extreme position. In the position shown, arm 68 completes a circuit comprising shunt 52, rheostat 62, a manually adjusted rheostat 5| and coil 49. In the extreme position opposite to that illustrated, arm 60 opens such circuit and connects coil 41 with cathode I4.

In the present embodiment, the elements which were already illustrated in Fig. I retain their respective functions and, in addition, regulator 31 generally performs, in a modified manner, the functions of regulator 22; rheostat 62 performs in a modified manner the functions of relays 35 and 36.

In operation, energization of line 6 and closure of circuit breaker 32 result in a flow of current through rectifier I3 as above described with reference to Fig. 1. Current then fiows through coil 44 in proportion to the voltage of line 1, 8 and another current fiows through coil 49 in proportion to the intensity of the current flow through rectifier I3, so that regulator 31 responds to the magnitude of the power output of rectifier I3 and tends to maintain such output at a predetermined constant value, except when the power fiowing through rectifier I3 is limited by the load to less than such predetermined value. If such output increases above such value, torque element 39 causes displacement of the movable tap of resistor 38 to increase the portion of resistor 38 inserted between cathode I4 and the neutral point of winding I8. The direct current voltage component impressed between cathode I4 and such neutral point increases accordingly, thereby causing the flow of current through rectifier I3 to decrease as is well known in the art. Such action continues until the output of rectifier I3 is adjusted to the desired value, and regulator 31 then remains in the position reached thereby until a change of load causes a further regulating action of regulator 31.

Closure of circuit breaker 32 causes closure of contacts 33 which establishes connection of motor 55 with battery 34 thereby setting motor 55 in motion to bring arm 60 of rheostat 62 from the extreme position shown to the other extreme position. During such operation, the resistance of the circuit including coil 49 is therefore progressively increased, thereby gradually increasing the value of the power output of the rectifier which regulator 31 tends to maintain. When the entire rheostat 62 is inserted in circuit with coil 49. arm 60 also effects connection of coil 41 with cathode I4 and thereafter opens the circuit of coil 49. Regulator 31 thus reconnected is then responsive only to the magnitude of the voltage of line I, 8 and regulates the flow of current through rectifier I3 to maintain such voltage at a predetermined constant value. Continued motion of motor 55 causes arm to open switch 53,

thereby deenergizing motor 55 which then stops. When circuit breaker 32 is opened, contacts 33 are also opened and contacts 51 are closed, thereby connecting motor 55 with battery 34 in a manner such as to cause motor 55 to return arm 60 into the position shown. In general, rectifier l3 would remain in favorable operating condition for a considerable period of time after interruption of the flow of current therethrough, so that upon reclcsure of circuit breaker 32 after a short interruption of the flow of current, it is not necessary to reestablish such fiow as slowly and gradually as when rectifier I3 is started after an extended interruption. By inserting resistor 53 in the circuit as shown in the drawings, the return movement of arm 30 to the position shown requires a longer period of time than is necessary for such arm to reach the other extreme position during starting. If circuit breaker 32 is opened for a short period of time, upon reclosure of such circuit breaker, arm 60 will therefore be in an intermediate position and the restarting operation of rectifier I3 will therefore be of reduced duration.

In the embodiment illustrated in Fig. 3, the regulation of the flow of current is again obtained by means of regulator 31 in which, however, coil 41 is then omitted, and coils 44 and 41 are connected in series. Ann 60 is again connected with cathode I4 and controls the connection of a modified rheostat 55 having both terminals thereof connected with coil 41, to regulate the fiow of current through such coil during starting operation and also during normal operation of the rectifier. ment, rectifier I3 is shown as provided with the usual cooling passages 64 through which a fiow of cooling liquid is obtained by suitable means such as a pump 66 driven by a motor 61 preferably energized from line 5 through contacts 33. The cooling fluid thus circulated is cooled by any suitable means such as radiator coil 69. The action of regulator 31 is controlled in response to the temperature of rectifier I3 by means of a suitable temperature responsive device inserted at a suitable point in rectifier I3 or in the cooling circuit thereof. Such device may be a bimetallic strip 1| in contact with the cooling fiuid issuing from passage 54 and provided with two insulated contacts 12 and 13 operable to selectively engage with arm 60 of rheostat 65.

In the present embodiment, the functions performed by the several elements already illus trated in Fig. 2 remain generally the same as in such figure, except that the operation of rheostat 55 is now obtained in response to the thermal conditions of rectifier I3 and that such rheostat is not directly controlled by closure of circuit breaker 32. As will appear from a description of the operation of the embodiment in 3, however, the system of such embodiment also controls the flow of current through rectifier I3, in time, at increasing values upon closure of circuit breaker 32.

In operation, upon energization of line I3 and closure of circuit breaker 32, a flow of current is established through rectifier I3 as above described to thereby energize line I, 8. The resistance of the circuit of coils 41 and 44, being at a minimum value due to direct connection of arm 63 with coil 41, energization of line 1, 8 produces, through coil 41, a fiow of current such as to immediately cause regulator 31 to move into the extreme position opposite to the position shown. The direct current voltage component In the present embodiiii impressed between cathode I4 and the neutral point of winding I8 is thereby made a maximum and the fiow of current through rectifier i3 is reduced to an extent such that the voltage of line 7, 8 is reduced to a predetermined value. Continued operation of rectifier l3 causes the temperature of the fluid circulating through passage 54 to gradually increase, thereby causing gradual deformation of bimetallic strip 1|. Such deformation causes contact 13 to engage with arm 60, thereby closing a circuit from battery 34 through arm 60, contact 13, switch 53 and field coil 54 and armature 55 of motor 55. Motor 55 then rotates and causes arm 60 to engage with the upper portion of rheostat 65, thereby increasing the resistance of the circuit of coils 41 and 44, such action continuing until arm 60 disengages contact 13. The circuit of motor 55 is then opened and the motor then stops. As a result of such operation, regulator 3'! regulates the flow of current through rectifier IS in a manner such that the voltage of line 7, 8 is then temporarily maintained at a predetermined value higher than the value of such voltage maintained immediately upon closure of circuit breaker 32. Upon further continued operation of rectifier l3, contact 13 will again engage with arm 513 to cause further adjustment of rheostat 65 to again vary the action of regulator 31. Such regulating action is repeated until rectifier l3, reaching a constant temperature, causes bimetallic strip H and arm to remain stationary. If circuit breaker 32 is opened or if the load carried by rectifier l3 decreases, bimetallic strip H tends to return to its original shape and causes engagement of contact 12 with arm 6!], thereby energizing motor to return arm toward the position shown. The motion of arm 60 may again be effected in steps controlled by successive disengagements and reengagements of contacts 12 with arm 50, and ceases when rectifier l3 reaches. a constant lower temperature or when arm 60 opens limit switch 59.

It may be desired to leave the adjustment of regulator 3'! constant when the temperature of the rectifier is within a predetermined range obtained during continued flow through the rectifier of all or of a substantial portion of the current which the rectifier is operable to carry, for the reason that the rectifier is then in the proper condition of temperature for carrying such currents without disturbance. Rheostat may accordingly be provided with a portion of no appreciable resistance engaging with arm 60 when thermostat H is at any temperature within such predetermined range. Deformations of bimetallic strip H and resulting motion of arm 50 are then without efiect on the resistance of the circuit of coil 41 and 44. If the temperature of rec'- tifier l3 increases beyond the permissible limit, further deformation of bimetallic strip H will cause arm 60 to engage with the lower portion of rheostat 55. Such action decreases the effective resistance of the rheostat in the circuit of coils il and 44. As a result of such action, regulater 37 controls the flow of current through rectifier l3 to maintain the voltage of line i, 3 at a lower value, and thereby tends to reduce the current intensity through rectifier I 3. Such action continues until the temperature of rectifier l3 becomes constant or until arm 60 opens limit switch 53.

In the embodiment illustrated in Fig. 4, rectifier I3 is shown provided with suitable evacuating means such as a pump 14 driven by a motor 16 .pressed on coil 86.

preferably energized from line B through contacts 33. The present system is made responsive to the value of the gas pressure in rectifier l3 by means of the well known Wheatstone bridge comprising two resistors 18 and 19 arranged in a gastight chamber communicating with the rectifier chamher, and two other resistors 81' and 82 arranged in air at atmospheric pressure. One diagonal of the bridge receives current from battery 34 and the other diagonal is connected with one coil 83 of a relay 84 of the balance type. Relay 84 is provided with a second coil 86 receiving a variable portion of the voltage of battery 34 through a rheostat 91 in series with a voltage divider 89 having the arm 90 thereof controlled jointly with the arm 60 of rheostat 62.

In the present embodiment the functions performed by the control elements already illustrated in Fig. 3 remain generally the same, except that rheostat 62 operates in response to pressure conditions of rectifier l3. In the present embodiment also the fiow of current through rectifier I3 is controlled, in time, at increasing values upon closure of circuit breaker 32 although rheostat 62 is not directly controlled by such circuit breaker.

In operation, line 6 being energized, upon closure of circuit breaker 32 the flow of current through rectifier I3 is initiated. Closure of contacts 33 causes energization of motor 16 which starts and drives pump 14. In general the pressure within rectifier l3 will be comparatively high at the time of closure of circuit breaker 32 due to the previous inoperation of pump 14. Even after a period of continued operation of rectifier l3, if circuit breaker 32 was opened to clear a disturbance such as a short circuit or a backfire, the amount of gases present in rectifier 13 will be comparatively high as a result of the momentary flow of excessive current through the rectifier. In addition, if the rectifier is assumed to be receiving its initial loading as in the so-called forming operation, initiation of flow of current therethrough will immediately result in liberation of a large amount of gases therein which make it necessary to progressively regulate the load carried by the rectifier.

Under such conditions of comparatively high gas pressure in rectifier l3, the current flowing through coil 83 is comparatively low. Arm 60 being in the position shown in thedrawings causes the highest possible portion of the voltage of line i, 8 to be impressed between cathode I4 and the neutral point of winding l8, thereby regulating the flow of current through rectifier It in a manner such as to cause the voltage of line 1, 8 to vary with the load in accordance with a predetermined characteristic curve of minimum values. Upon decrease of the pressure within rectifier l3 due to continued action of pump 14, the current through coil 83 increases and the attraction of coil 83 on the armature of relay 84 overcomes the attraction of coil 86, thereby causing the armature to close contact 88. A circuit is thereby closed from battery 34 through contact 88, switch 53 and field coil 54 and armature 56 of motor 55. Motor 55 starts and drives arm 60 of rheostat 62, thereby decreasing the direct current voltage component impressed between cathode l4 and neutral point of winding l 8 and causing the voltage of line I, 8 to follow a characteristic curve of higher values. Motor 55 also drives arm 90 of rheostat 89 thereby increasing the voltage im- Such action continues until the combined attractions of coils 83 and 86 on the armature of relay 84 cause contact 88 to reopen, thereby causing motor 55 to stop. Such action is repeated until the pressure within rectifier I3 is decreased to a constant value or until arm 98 opens limit switch 53, the voltage of line I, 8 then being no longer regulated. Upon increase in the pressure within rectifier l3 due to the unavoidable leakage occurring over periods of inoperation or due to the liberation of gases resulting from the flow of current through the rectifier, the current through coil 83 decreases and the action of coil 88 overcomes that of coil 83 to cause the armature of relay 84 to close contacts 81. Motor 55 is thereby energized to return arms 60 and 98 toward the position shown, such action continuing until the flow of current through coil 86 is decreased by movement of arm 98 to an extent such as to cause reopening of contact 81. The flow of current through rectifier I3 is then again regulated in accordance with a lower characteristic curve. Such action is repeated until the pressure within rectifier [3 reaches a constant higher value or until arm 9|! opens switch 59.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a system for controlling the flow of electric current, electron discharge means to be controlled, and means responsive to a pressure condition of the first said means for causing the flow of current therethrough to be progressively varied.

2. In a system for controlling the flow of electric current, electron discharge means to be controlled, means for controlling the initiation of flow of current through said discharge means, means responsive to an electrical condition of said system for regulating the flow of current through said discharge means, and means comprising an element of the second said means and controlled thereby for varying the adjustment of the third said means to progressively vary the action thereof at a predetermined rate in dependent of the rate of movement of the second said means.

3. In a system for controlling the flow of electric current, electron discharge means to be controlled, discharge controlling means for said discharge means, means responsive to an electrical condition of said system for controlling the second said means, means for controlling the initiation of flow of current through said discharge means, and means comprising an element of the fourth said means and operable thereby to progressively vary the action of the third said means at a predetermined rate independent of the rate of movement of the fourth said means.

l. In combination with an electron discharge device having a cathode and an anode constituting electrodes for the flow of current therebetween, of means comprising a control electrode associated with said anode operable to regulate the magnitude of said flow of current, and means responsive to a thermal condition of said device for controlling the said operation of the first said means.

5. In combination with an electron discharge device having a cathode and an anode constituting electrodes for the flow of current therebetween, of means comprising a control electrode associated with said anode operable to cause said flow of current to be progressively varied, and means responsive to a pressure condition of said device for controlling the said operation ofthe first said means.

6. In an electric current conversion system, the combination of an electron discharge device comprising acathode, an anode constituting with said cathode electrodes for the flow of current therebetween, and a control electrode associated with said anode operable to cause said flow of current to be progressively varied, and means operable responsive to an operating condition of said system for controlling the said operation of the said control electrode in such sense as to cause the magnitude of said current to be progressively increased at a predetermined rate independent of the rate of movement of said means.

7. In an electric current conversion system, discontinuously controllable electron discharge means, means for controlling the initiation of flow of current through the first said means and for causing the flow of said current to be progressively increasingly varied at a predetermined rate, and means operable responsive to an operating condition of said systemfor controlling the said flow of current through the first said means.

8. In an electric current conversion system, discontinuously controllable electron discharge means, means for controlling the initiation of flow of current through the first said means, and current responsive means operable responsive to variations in the magnitude of the current flowing through said device and controlled by the second said means for causing the said flow of current to be progressively increased at a predetermined rate.

9. In an electric current conversion system, an electron discharge device, means operable to one position thereof to control thereat the initiation of flow of current through said device and operable to another position thereof to cause interruption of said current, means comprising an element of said device for controlling the operation thereof in such sense as to cause the magnitude of said current to be varied, means operable from one to another position thereof to affect the operation of the second said means in such sense as to cause the magnitude of said current to be progressively increased at a predetermined rate, and means operable responsive to operation of the first said means to the said one position thereof to cause said operation of the third said means and operable responsive to said operation of the first means to the said another position thereof to cause operation of the third said means to the said one position thereof.

10. In an electric current conversion system, an electron discharge device, means operable to one position thereof to control thereat the initiation of flow of current through said device and operable to another position thereof to cause interruption of said current, means comprising an element of said device for controlling the operation thereof in such sense as to cause the magnitude of said current to be varied, means opera ble from one to another position thereof at such a rate as to affect the operation of the second said means in such sense as to cause the magnitude of said current to be progressively increased at a predetermined rate, and current responsive means operable responsive to operation of the first said means to the said one position thereof to cause said operation of the third said means.

11. In an electric current conversion system, an electron discharge device, means operable to one position thereof to control thereat the initiation of flow of current through said device and operable to another position thereof to cause interruption of said current, means comprising an element of said device for controlling the operation thereof in such sense as to cause the magnitude of said current to be varied, means movable from one to another position thereof at such a rate as to affect the operation of the second said means in such sense as to cause the magnitude of said current to be progressively increased at a predetermined rate, and means operable responsive to operation of the first said means to the said one position thereof to cause said movement of the third said means and operable responsive to operation of the first said means to the said another position thereof to cause movement of the third said means to the said one position thereof at a predetermined rate differing from the said rate of movement thereof to the said another position thereof.

12. In an electric current conversion system, an electron discharge device comprising an anode and a cathode constituting spaced electrodes for the flow of current therebetween, means for controlling the initiation of said fiow of current, means comprising an element of said device for controlling the said flow of current, means comprising an element responsive to said flow of current for affecting the action of the second said means in such sense as to cause said current to be maintained at substantially constant magnitude, and current responsive means operable responsive to said operation of the first said means for afiecting the action of the third said means in such sense as to cause said current to be progressively increased at a predetermined rate.

13. In an electric current conversion system, the combination. with an electric current supply circuit, a load circuit, an electron discharge device comprising an anode and a cathode interconnecting said circuits and constituting spaced electrodes for the flow of current between said circuits, and means controlling the initiation of said flow of current, of means comprising an element of said device for controlling the magnitude of said current, means comprising an element responsive 'to said flow of current for controlling the said action of the second said means, and current responsive means operable responsive to operation of the first said means for affecting the operation of the third said means in such sense as to cause the magnitude of said current to be progressively increased at a predetermined rate.

14. In an electric current conversion system, the combination with an electric current supply circuit, a load circuit, an electron discharge device comprising an anode and a cathode interconnecting said circuits and constituting spaced electrodes for the flow of current between said circuits, and means controlling the initiation of said flow of current, of means comprising a control electrode of said device for controlling the magnitude of said current, means comprising an element responsive to the fiow of said current in one of said circuits for controlling the said action of the second said means, and current responsive means operable responsive to operation of the first said means for aiTecting the action of the third said means in such sense as to cause the magnitude of said current to be progressively increased at a predetermined rate.

15. In an electric current conversion system, the combination of an electric current supply circuit, a load circuit, an electron discharge device comprising an anode and a cathode interconnecting said circuits and constituting spaced electrodes for the flow of current between said circuits, means comprising an element of said device for controlling the magnitude of the voltage or" said load circuit, and means operable responsive to an operating condition of said system for controlling the said operation of the first said means in such sense as to cause the magnitude of the said voltage to be progressively increased at a predetermined rate.

16. In an electric current conversion system, the combination of an electric current supply circuit, a load circuit, an electron discharge device comprising an anode and a cathode interconnecting said circuits and constituting spaced electrodes for the flow of current between said circuits, means comprising an element of said device for controlling the magnitude of the voltage of said load circuit, means for controlling the operation of the first said means comprising elements respectively responsive to variations of the current and of the voltage of said load circuit, and means for aiTecting the operation of the secend said means in such sense as to thereby cause the first said means to operate in such manner as to cause the magnitude of the power output of said device to be progressively increased.

17. In an electric current conversion system, the combination of an electric current supply circuit, a load circuit, an electron discharge device comprising an anode and a cathode interconnecting said circuits and constituting spaced electrodes for the flow of current therebetween, means for initiating the said fiow of current, means comprising an element of said device for controlling the magnitude of the voltage of said load circuit, means for controlling the operation of the second said means comprising elements respectively responsive to the magnitude of the current and the voltage of the said load circuit, and means operable responsive to operation of the first said means for affecting the operation of the third means in such sense as to thereby cause the operation of the second said means to be modified in such sense as to cause the magnitude of the power output of the said device to be progressively increased at a predetermined rate.

HAROLD WINOGRAD. 

